1. Field of the Invention
This invention relates generally to a reproducing system, and more particularly to a reproducing system which has an automatic head scan tracking system.
2. Description of the Prior Art
In general, in a video tape recorder (VTR) video signals are recorded in plural record tracks on a magnetic tape, which, tracks extend across the longitudinal direction of the tape and are arranged in parallel with one another with a predetermined distance between adjacent tracks.
In order to obtaining a high recording density with such a VTR, it is necessary to narrow the pitch of the recording tracks and also the width of each track. In such a case, if the normal rotation speed of a rotary magnetic head is selected, that is, a speed that is the same as that of an ordinary VTR, the tape transportation speed can be made low. Thus, long time recording becomes possible. If the tape transporation speed is selected to be the same as that of the ordinary VTR, then the rotation speed of the rotary magnetic head is made high, and wide frequency signals can be recorded. In this case, even if the width of recording tracks is made narrow, due to the fact that the signal-to-noise ratio S/N is less deteriorated, the overall quality of reproduced signals can be made high.
In fact, however, the recording tracks formed by the rotary magnetic head are not always straight and the linearity of recording tracks is deteriorated by the distortion of the tape caused by, for example, stretching of the tape and so on. Accordingly, when such recording tracks are scanned by the rotary magnetic head, a so-called tracking error is produced and hence the level of reproduced signals is varied. This defect becomes more noticeable as the track width becomes narrower.
For this reason, if the track width of the reproducing head is made greater than that of the recording head, the above defect can be removed. In this case, however, a possible disadvantage is that a signal is reproduced from an adjacent track and hence the quality of reproduced signals is deteriorated.
For this reason, a method has been proposed in which the rotary magnetic head is moved or displaced by an electromechanical transducer in the direction that is transverse to the longitudinal direction of the tape to carry out an automatic head scan tracking. With this method, a tracking error signal is provided by intentionally deflecting or displacing the magnetic head by a small amount in each direction from the track center in a sinusoidal manner so as to create a carrier amplitude modulation of a known frequency and phase. This tracking error signal is fed back to the transducer to complete a tracking servo loop. Accordingly, even if the recording tracks are curved, the reproducing head can scan the recording tracks. With this method, however, a carrier amplitude modulation is always created in the reproduced video signal, so that the phase of the reproduced video signal is changed thereby, and especially there is caused a phase error in the chrominance signal. Further, the apparatus for achieving the above method becomes complicated in construction.